Apparatus for accurate die-cutting

ABSTRACT

Inaccurate cuts often occur in paperboard blanks passing between a pair of cooperating die and anvil cylinders because of anvil cylinder wear, irregular blank velocity, and other factors. Such inaccuracies are reduced by driving the die cylinder at a preselected angular velocity and driving the anvil cylinder at an angular velocity proportional to the angular velocity of the die cylinder with the preselected proportion being maintained during changes in angular velocity of the die cylinder. The preferred apparatus includes a first mechanical transmission having a primary input driven by the die cylinder and a secondary input driven by a second mechanical variable-ratio transmission for driving the anvil cylinder at an angular velocity corresponding to the angular velocity of the die cylinder but with the anvil cylinder velocity being selectively variable to provide an anvil cylinder velocity selectively proportional to the velocity of the die cylinder. Additionally, a slip clutch is preferably interposed between the drive for the die cylinder and the first transmission to permit the anvil cylinder to change its rotational position relative to the rotational position of the die cylinder upon the occurence of excessive torque.

United States Patent [191 Leaseburge et 'al.

[ Sept. 3, 1974 1 APPARATUS FOR ACCURATE DIE-CUTTING [73] Assignee: Koppers Company, Inc., Pittsburgh,

[22] Filed: Oct. 29, 1973 [21] Appl. No.: 410,675

Primary ExaminerDonald R. Schran Attorney, Agent, or Firm-Olin E. Williams; Oscar B. Brumback; Boyce C. Dent [5 7 ABSTRACT Inaccurate cuts often occur in paperboard blanks passing between a pair of cooperating die and anvil cylinders because of anvil cylinder wear, irregular blank velocity, and other factors. Such inaccuracies are reduced by driving the die cylinder at a preselected angular velocity and driving the anvil cylinder at an angular velocity proportional to the angular velocity of the die cylinder with the preselected propor-.

tion being maintained during changes in angular velocity of the die cylinder. The preferred apparatus includes a first mechanical transmission having a primary input driven by the die cylinder and a secondary input driven by a second mechanical variable-ratio transmission for driving the anvil cylinder at an angular velocity corresponding to the angular velocity of the die cylinder but with the anvil cylinder velocity being selectively variable to provide an anvil cylinder velocity selectively proportional to the velocity of the die cylinder. Additionally, a slip clutch is preferably interposed between the drive for the die cylinder and the first transmission to permit the anvil cylinder to change its rotational position relative to the rotational position of the die cylinder upon the occurence of excessive torque.

9 Claims, 4 Drawing Figures PATENIED W I 3.832.926 SHEET 20$ 2 FIG. 3

APPARATUS FOR ACCURATE DIE-CUTTING CROSS REFERENCES TO RELATED APPLICATIONS This invention is an improvement over co-pending application Ser. No. 319,163 filed Dec. 29, 1972 by Clyde B. Garrett et al for Method and Apparatus For Accurate Die-Cutting and assigned to the assignee of the present invention.

BACKGROUND OF THE INVENTION 1. Field of the Invention This invention relates generally to cutting and more particularly to rotary tools with cooperating rotary resilient anvil back-up surfaces.

2. Description of the Prior Art The problems associated with accurate die-cutting discussed in the aforementioned application have been mostly overcome by use of the methods and apparatus claimed in such application. However, the earlier invention required considerable electrical control apparatus to cause the anvil cylinder to track the velocity of the die cylinder and to provide for variable proportional velocities between the two cylinders, particularly in order to achieve the fine degree of accuracy desired. This invention provides a more consistently attainable fine degree of accuracy by use of a mechanically positive transmission arrangement which is also less complex than the earlier invention. In addition, it has been found that the use of certain die-cutting rules, particularly a great number of laterally extending rules for making horizontal cuts, often causes considerable drag on the anvil cylinder as the rules penetrate the anvil covering. The drag is especially pronounced when the anvil cylinder is being rotated in excess of about 1 percent above or 1 percent below the velocity of the die cylinder. With a hard connection between the two cylinders, the result is sometimes torn or at least excessively worn anvil cylinder coverings. Such drag manifests itself by requiring an excessive torque requirement for rotating the anvil cylinder to maintain its selected velocity proportional to the velocity of the die cylinder. This invention provides for slippage in the drive train between the two cylinders during moments of excessive torque requirements thereby reducing the amount of wear of the anvil covering.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide positive acting apparatus for controlling the accuracy of cuts made in paperboard blanks both as to their length and to their location in the blank and, although not essential, to provide for slippage in the drive train between the die cylinder and anvil cylinder during moments of excessive torque.

These and other objects are achieved by driving the die cylinder at a selectedangular or tangential velocity and driving the cooperating anvil cylinder at a tangential velocity that is selectively proportional to the velocity of the die cylinder to control the velocity of the blank passing between the cylinders thereby compensating for irregular velocities imposed on the blank from the characteristics of the cutting rules and other factors and to control the velocity of the anvil cylinder to be nearly identical to the velocity of the die cylinder even though the anvil cylinder circumference may be less than nominal with respect to the effective diameter of the cutting rules. Preferably, the selected proportional velocity of the anvil cylinder is maintained during speed changes of the entire machine.

The preferred apparatus includes a mechanical transmission means, such as a harmonic drive type, with a primary input connected to the die cylinder which tracks the velocity of the die cylinder and an output connected to the anvil cylinder that is responsive to the primary input for rotating the anvil cylinder at a velocity generally corresponding to the velocity of the die cylinder. This arrangement also includes a mechanical variable-ratio transmission means responsive to the velocity of the die cylinder for supplying a secondary input to the first transmission to provide a selectively variable output with respect to the primary input for selectively controlling the proportional velocity of the anvil cylinder with respect to the die cylinder.

Several types of mechanical transmissions may be used as the prime driver of the anvil cylinder, their common characteristics being that their outputs are responsive to both a primary input and a secondary input to provide speed tracking and selectively variable control of the output. However the transmission preferred for use as the first transmission in the present invention is a harmonic drive'type designated HDC-4M80-2 manufactured by USMCorporation, Gear Systems Division, 81 Bay State Road, Wakefield, Mass. 01880. Such transmission may be easily modified by those skilled in the art to provide the desired input to output speed ratio, gear mounting arrangement, transmission mounting arrangement, and the like.

The transmission preferred for use as the second transmission to provide the secondary input to the first transmission for varying the percentage difference in speed of the output of the first transmission is a positive infinitely variable type designated P.I.V. variable speed, size 0, ratio 4:1 manufactured by F MC Corporation, Link Belt Enclosed Drive Division, 2045 Hunting Park Ave. Philadelphia, Pa. 19140.

The foregoing apparatus provide a means for controlling the accuracy of cut sizes and locations in the blank, preferably to an accuracy of at least plus or minus 0.1 percent which amounts to an accuracy of about 0.038 inches in a blank 38 inches long which accuracy is not consistently attainable with known rotary die-cutters.

The above and further objects and novel features of the invention will appear more fully from the following detailed description when the sameis read in connection with the accompanying drawings. It is to be expressly understood however, that the drawings are not intended as a definition of the invention but are for the purpose of illustration only.

BRIEF DESCRIPTION OF THE DRAWINGS In the drawings wherein like parts are marked alike:

FIG. 1 is a schematic illustration in front elevation of a rotary die-cutter including a pair of cooperating die and anvil cylinders and showing the preferred arrangement for driving the anvil cylinder at a velocity corresponding to the velocity of the die cylinder and at a selectable proportion thereto;

FIG. 2 is a schematic illustration in side elevation of the arrangement of FIG. 1;

FIG. 3 is an enlarged view in cross-section of a portion of the cylinders of FIG. 1 showing the arrangement of the transmissions in greater detail; and

FIG. 4 is a sectional view of a portion of the harmonic transmission of FIG. 7 taken along line IV-IV.

DESCRIPTION OF THE PREFERRED EMBODIMENT FIG. 1 schematically illustrates a conventional rotary die-cutter adapted for operation in accordance with the apparatus of the present invention. The die-cutter generally denoted by numeral 10 includes a pair of spaced side frames 12 and 14 between which are mounted a pair of cooperating cylinders, the upper of which is the die cylinder 16 and the lower of which is the anvil cylinder 18. A cross-tie 20rigidly connects the frames 12 and 14. The cylinders 16 and 18 include individual journals 24, 26, 28 and 30 extending through conven tional bearings 32 in frames 12 and 14 which permit the cylinders to freely rotate about their axes.

The die cylinder 16 is constructed to carry conventional cutting and scoring rules 34 mounted on an arcuate plywood backing or die blanket 35 secured to the cylinder; the anvil cylinder is usually completely covered by a relatively thin resilient cover 36 such as polyurethane plastic. This cover may be bonded to a metal drum portion 38 of cylinder 18 but is preferably mechanically fastened thereto to permit replacement of extremely worn covers. An arrangement of this nature is shown and described in Sauer U.S. Pat. No. 3,577,822 although other similar constructions will work equally well with the present invention.

As the cylinders 16 and 18 rotate, paperboard blanks 40 (FIG. 2) are successively advanced between them in lineal register with the rotating rules 34 which cut and score the blanks. The radial height of the scoring rules (well-known and not specically shown) is such that their rounded outer edges make depressions in the blanks which permit the finished blanks to be folded along the score lines. The cutting rules 34 usually have serrated edges (not shown); their radial height (from the surface of the die cylinder 16) is such that their outer serrated edges penetrate through the blank 40 and slightly into the cover 36 as they pass through radial alignment with the axis of the anvil cylinder such as shown in FIG. 3.

The length of the vertical cuts (those cuts extending in the direction of blank travel) made in blanks 40 is first determined by the arcuate length of the cutting rules. However, the actual length that is cut may be longer or shorter than the desired length if the blank is accelerated or decelerated as it passes between the cylinders 16 and 18. For example, if die cylinder 16 is driven at a constant selected velocity by drive motor 56 (.to be subsequently explained), then cutting rules 34 will rotate at a constant velocity. Should the blank 40 be accelerated by penetration of the leading tip of rule 34 in blank 40, then a length of paperboard greater than the length of rule 34 will pass between the cylinders before the rule passes out of the blank. This results in a cut longer than the length of rule 34. Conversely, should blank 40 he decelerated. then a cut shorter than the length of rule 34 will be made.

It can also be seen that acceleration or deceleration of blank 40 will similarly result in the spacing, in the direction of blank travel, between horizontal cuts (those cuts extending transversely to blank travel) being too long (if acceleration occurs) or too short (if deceleration occurs).

In accordance with this invention, the surface velocity of the anvil cylinder cover is controlled by driving the anvil cylinder 18 at an angular velocity selected to cause the cover 36 to exert sufficient influence on blank velocity to overcome any inaccuracies of cut length and location in the blanks. This maybe accomplished in accordance with the following description.

Referring back to FIG. 1, journal 24 of die cylinder 16 includes a conventional spur tooth gear 50 secured for driving rotation therewith; gear 50 is driven by another gear 52 secured to the output shaft 54 of a main drive motor 56 for the die-cutter 10. Thus, energization of motor 56 will rotate die cylinder 16 at the speed selected by use of a conventional rheostat motor control 56a.

It should be understood that the die cylinder 16 is usually driven by gearing connected to a conventional feeder (not shown) that feeds blank 40 in sequence between cylinders 16 and 18. For example, in FIG. 2 a pair of pull rolls 58 and 60 conventionally grip the blanks 40 as they are fed therebetween and feed them between cylinders 16 and 18. These pull rolls may be driven from adjacent gearing on the blank feeder and in turn drive the die cylinder by similar conventional gearing. This gearing has been omitted for clarity and the cylinder 16 is shown as being driven by motor 56 for simplicity since it is immaterial to the present invention whether the cylinder 16 is synchronously driven by the motor or by adjacent machinery. Likewise, the normal gear guards, lubrication system and the like have been ommitted since they form no part of the invention and are well known by those skilled in the art.

The journal 28 of anvil cylinder 18 extends into and is coupled to a mechanical transmission 70, which is better shown in FIG. 3. Transmission also includes a primary input spur gear 76 which is in mesh with gear 50 (see FIG. 1). Thus, motor 56 rotates cylinder 16 and cylinder 18 through transmission 70. Thus, as the motor 56 is accelerated or decelerated, the velocity of cylinder 18 will follow or track the velocity of cylinder 16. Normally, an operating speed will be selected for motor 56 and anvil cylinder 18 will follow or track the speed selected.

However, the output speed of transmission 70 may be changed relative to the speed of die cylinder 16, that is, the transmission output journal 28, which is also the input to anvil cylinder 18, can be made to run faster or slower than the input to the die cylinder 16 from motor 56. This is accomplished by rotation of secondary input shaft 130 from'a positive infinitely variable transmission (such as previously described and herinafter referred to as P.I.V. 90) at a selected speed to add to the speed of the output journal 28 as will be later explained.

Before further description of the P.I.V. 90, it is better to understand the construction and operation of harmonic transmission 70 which is illustrated in detail in FIG. 3.

The harmonic drive 70 includes a flanged rigid circular spline 102 mounted to the side of primary input gear 76 by screws-106 in the ordinary manner. Gear 76 is mounted on a roller bearing 108 secured to the end of journal 28 so as to be freely rotatable thereabout and is in mesh with gear 50 (as shown in FIG. 1) so as to be driven thereby; this arrangement comprises the primary input of harmonic drive 70.

A flexible circular spline 112 is nested within rigid spline 102. One end of flexible spline 112 is closed by a radially extending end portion 114 having a central opening surrounding a reduced shoulder portion 116 of journal 28. End portion 114 is secured for rotation with journal 28 by washers 118 disposed on both sides of the end portion 114 with screws 120 passing through both washers 118 and end portion 114 and into journal 28 in the ordinary manner. This construction also axially secures bearing 108 on reduced shoulder portion 116 of journal 28.

The open end of flexible spline 112 includes external spline teeth 122 around its outer periphery. These teeth are adapted to mesh with corresponding internal spline teeth '124 formed around the inner periphery of rigid spline 102. This is further illustrated in FIG. 4.

P.I.V. 90 is mounted by screws 128 to a support 129 secured to and spaced from the side frame 12; P.I.V. 90 includes an output shaft 130 extending in coaxial alignment with the central axis of flexible spline 112.

Shaft 130 includes a reduced shoulder portion 140 upon which a wave-generator cam 142 is securedfor rotation therewith by a conventional shaft key 144, washer 146, and screw 148 in the ordinary manner.

An elliptical roller bearing 150 is secured, as for example by a press fit, around the periphery of cam 142 which is also elliptical as illustrated in FIG. 4. The major diameter of the bearing 150, that is, the portion opposite the lobes of cam 142, urges the external spline teeth 122 into meshing engagement with internal spline teeth 124.

Operation of the harmonic transmission 70 is, briefly, as follows. Primary input driving gear 76 is secured to the rigid spline 102, as previously described, and is adapted for rotation around journal 28 by means of bearing 108. Journal 28 is secured for rotation with flexible spline 112. The wave-generator (comprising cam 142 and bearing 150) is continuously rotated by the P.I.V. output shaft 130 extending from P.I.V. 90 to change the angular velocity between gear 76 and anvil cylinder 18 when cylinder 18 is to be rotated faster or slower than die cylinder 16.

It should be understood that the flexible spline 112 is made of thin flexible metal (although plastic materials can be used where the torque to be transmitted is small) so that the wave-generator can deflect the external teeth 122 into engagement with internal teeth 124 of rigid spline 102 at the two points opposite the lobes of cam 142. Thus, rotation-of the wave-generator will result in a continuously moving waveform transferred to flexible spline 112. This causes the flexible spline 112 to rotate with a greatly reduced tangential motion. A full rotation of the wave-generator by output shaft 130 (which can also be considered as a secondary input into transmission 70) will produce a rotation of flexible spline 112 through a distance equal to the difference between the circumference of the rigid spline 102 and the circumference of flexible spline 112. Consequently, the actual reduction ratio can be obtained by dividing the difference between the two circumferences into the circumference of the flexible spline 112. Since the spline teeth on both the flexible spline 112 and rigid spline 102 have the same circular pitch, the actual number of teeth on each can be used as the circumferential measurement; the reduction ratio of any unit can be computed by dividing the difference between the number of teeth on the two splines into the number of teeth on the output member (flexible spline 112). For example, if the rigid spline 102 has 202 teeth and the flexible spline 112 has 200 teeth, the ratio would be 200/202 200 200/2 Thus, when the harmonic drive is used in the ordinary manner with the rigid spline 102 fixed and the input going into wavegenerator 142, the output of flexible spline 112 would be one revolution for each hundred revolutions of the input shaft 130.

However, as used in the present invention, the wavegenerator 142 is rotated continuously by shaft and rigid spline 102 is rotated continuously by gear 76; thus, the rigid spline 102 constitutes a primary input which rotates at machine speed, that is, the same speed as the die cylinder 16, and cam or wave-generator 142 constitutes a secondary input which rotates at the speed of P.I.V. output shaft 130; flexible spline 112 constitutes the output with its rotation transferred to anvil cylinder 18 through journal 28 as previously described. Thus, the output of flexible spline 112 is at the ratio of 2021200 (or 101:100), that is, 101 revolutions for each 100 revolutions of input by rigid spline 102.

Since the cylinders 14 and 16 theoretically rotate at the same-circumferential velocity as the lineal velocity of the blank being printed, it is necessary to establish the foregoing ratio in reverse between the cylinder driving gears 50 and 76. For example, if gear 50 on die cylinder 14 has 100 teeth, then gear 76 on anvil cylinder 18 will have 101 teeth to reduce its velocity by the same amount that the velocity of flexible spline 112 is increased by rigid spline 102. In this manner, the circumferential velocity of the cylinders 16 and 18 is made equal to the lineal velocity of the blank 40 being cut when the wave-generator 142 is held stationary.

However, as arranged in the present invention, the output shaft 130 from P.I.V. 90 rotates continuously since its external input rotates continuously. This input is provided by a conventional spur tooth gear 51 mounted for rotation with the journal 24 of die cylinder 16; a similar gear 53 is mounted in the usual manner for rotation with an input shaft 55 extending from P.I.V. 90. The P.I.V. is mounted to support 129 so that input gear 53 meshes with drive gear 51 and is driven thereby. The ratio of gears 51 and 53 is selected to provide the required output speed for shaft 130 to harmonic drive 70, it being understood that the output speed of shaft 130 can be manually selected over the design range of the P.I.V. with aconstant input speed provided by input shaft 55. Manual selection is accomplished by turning ahandwheel 57 on P.I.V. 80. Since the internal construction of P,l.V. type transmissions and their operation are well known, no further description in this regard is believed necessary.

As previously mentioned, the anvil cylinder 18 is to be rotated either slower or faster than the die cylinder 16 depending on the characteristics of the die-cutting being performed on the blanks. The amount of underspeed or overspeed may be as much as 10 percent below or above the speed of the die cylinder; however 2 percentbelow and 2 percent above is usually sufficient and is easily attainable with the transmission arrangement of the present invention. However, it should be understood that the output shaft 130 of P.I.V. 90 always rotates in one direction. Therefore, it is necessary to select the ratio of gears 50 and 76 so that when the P.I.V. ratio is set by handwheel S7 for a minimum input to output speed change, the output speed from transmission 70 to journal 28 is such that the anvil cylinder 18 will be rotating at, for example, 2% below the speed of die cylinder 16. Then, as the handwheel 57 is used to increase the output speed of the P.I.V. 90, it will in turn add to the speed of harmonic transmission 70 to increase the speed of anvil cylinder 18. The design ratio of P.I.V. 90 is selected so that when it is manually adjusted to provide the greatest input to output speed difference, the output shaft 130 will add a sufficient number of revolutions to the harmonic transmission 70 to increase its output speed to the anvil cylinder 18 to cause the cylinder speed to increase from 2 percent below to 2 percent above the speed of the die cylinder 16. In view of the example set forth hereinabove, the required gear ratios for the various gears can easily be selected by those skilled in the art to achieve the desired output speed of transmission 70.

A harmonic drive with a 100:] ratio provides a highresolution phase adjustment. For example, one revolution of the wave-generator 142 produces an angular phase shift of 36 of spline 112 with respect to spline 102. If the cylinder 18 is a nominal 50 inches in circumference, one revolution of wave-generator 142 by secondary input shaft 130 produces a circumferential shift of 0.5 inches of the cylinder 18 relative to the nominal circumference of cylinder 16. The wave-generator 142 may be easily rotated a fraction of a revolution per one revolution of gear 76 to thereby produce a phase shift of a few thousandths of an inch so that very accurate control of the angular velocity of cylinder 18 can be obtained.

As illustrated in FIG. 1, the drive gear 52 on main motor shaft 54 meshes with and drives gear 50 on journal 24 of die cylinder 16 to drive the cylinder at the desired speed. Gear 50 also meshes with and drives primary input gear 76 on harmonic drive 70. As previously explained, the other gear 51 on journal 24 drives the input gear 53 to P.l.V. 90 and P.I.V. output shaft 130 adds to the output speed of harmonic drive 90 by an amount selected with handwheel 57 on P.I.V. 90. In this manner, the anvil cylinder 18 tracks the speed of die cylinder 16 but at a selected proportion thereto. Even if the speed of die cylinder 16 is changed by changing the speed of motor 56, such as by a conventional rheostat control 56a, the anvil cylinder will continue to track the newly selected speed of die cylinder 16 at the selected proportional speed.

However, the direct engagement of gear 50 with gear 76 forms a hard connection between the die and anvil cylinders. It has been found, as previously mentioned, that some arrangements of die-cutting rules may cause extreme wear or even tear the resilient covering 36 on cylinder 18 during penetration of the cutting rules 34 therein, particularly when a considerable difference in speed between the cylinders is present.

To alleviate this condition, the hard connection between gears 50 and 76 may be replaced by a soft connection. This is preferably accomplished by the arrangement shown in FIG. 3. In this arrangement, motor drive gear 52 drives die cylinder gear 50a which is keyed to journal 24 as shown; however gear 50a does not drive the primary transmission input gear 76. Instead, another gear 50b on journal 24 meshes with and drives input gear 76.

To achieve a soft connection, gear 50b is mounted for free rotation about a conventional bearing or bushing 61 on journal 24. A conventional electric clutch 63 is also mounted on journal 24 alongside gear 50b. Clutch 63 includes a driven hub 65 keyed to journal 24 and a driving hub 67 secured to gear 50b such as by screws 69. Driven hub 65 turns with journal 24 and, with current applied to clutch 63, driving hub 67 turns gear 50b which in turn rotates transmission input gear 76. However, in the event that cutting rule penetration or other factors cause considerable drag on the anvil cylinder 18 which then requires excessive torque to rotate the anvil cylinder, the needed torque, when it exceeds the torque rating of the clutch, will cause the clutch hubs to slip relative to one another. In this situation, the die cylinder 16 continues to rotate but anvil cylinder 18 is permitted to slip because gear 50b will momentarily stop rotating. As the torque requirement lessens, the clutch 65 and 67 will again engage and proper operation will continue.

It should be noted that die cylinder gear 50 is preferably not mounted directly to a clutch to obviate the need for a gear 50b since this would drive the anvil cylinder 18 and permit the die cylinder 16 to slip; this would result in loss of registration between the cutting rules and the blank, that is, the die cylinder 16 must remain in registration with the main drive train that feeds the blanks between the cylinders.

Although any number of torque limiting devices may be chosen to provide the soft connection desired, even purely mechanical ones, the electric clutch illustrated was chosen as being the most suitable and may be, for example, one identified as an electromagnetic multiple disc clutch, model FOV lO manufactured by the Formsprag Company, 23601 Hoover Road, Warren, Michigan 48090.

It should also be understood that the arrangements shown in FIGS. 1 and 2 are simplified schematic illustrations to facilitate explanation and understanding of the invention. In actual practice it may be necessary, in order to fit the transmissions in the space available or to achieve the desired gear ratios, to indirectly connect the transmissions to the die and anvil cylinders through a series of idler gears. And, as previously mentioned, the transmissions may also be connected to a main drive gear train rather than to a drive motor as shown. However, locating and connecting equipment by use of idler gears and the like is customary and well understood by those skilled in the art and does not adversely affect the construction and operation of the present invention as illustrated in the figures.

OPERATION,

To operate the machine of the present invention, the desired scoring and cutting rule die 35 is selected and mounted on die cylinder 16 in the customary manner. A stack of blanks 40 is placed in the feeder (not shown) and the blanks are advanced individually by advancing means such as by pull rolls 58 and through the diecutter 10 between cylinders 16 and 18. Preferably, the first few blanks are fed through the machine at a jog speed to be certain that the cutting die is in near regis tration with the desired location of scores and cuts in the blank. The rheostat control 56a may be used to control the speed of drive motor 56. If the scores and cuts are not in register, the die may be repositioned around the circumference and/or along the length of the cylinder until registration is achieved.

Thereafter, a production speed of the machine is selected and blanks are fed through the machine. As the first die-cut blanks emerge, they may be visually inspected for accurate cuts such as by comparing their location with respect to printed indicia which may be present on the blanks. However, a more accurate procedure is to stop the machine (to prevent accumulation of inaccurate blanks) and measure one of the die-cut blanks for accurate location of the creases and cuts such as by using a tape measureQShould measurement reveal that the cuts are too far ahead of where they should be, for example, this would indicate that the velocity of the blank is being impeded in its travel through the machine for one or more of the previously mentioned reasons. Therefore, the handwheel 57 on P.I.V. 90 is rotated in the proper direction to increase the output speed of harmonic 90 to cause the anvil cylinder 18 to run faster as previously explained. Blanks are again run through the machine at production speed and another blank measured for accuracy of the cuts. This step is repeated until the cuts occur at the exact location desired. As the operator becomes experienced in using the invention, he will soon be able to judge at what position the handwheel 57 should be rotated to cause the cuts to move along the blank to the desired location without making many trial and error selections.

Of course, if the cuts shouldoccur behind the desired location, this would indicate that the blank is being accelerated'as it passes between the cylinders 16 and 18 and therefore, the handwheel 57 would be rotated toward the subtract position in a manner similar to that described above.

The input to output ratios of the transmissions 70 and 90 are preferably selected to cause the anvil cylinder 18 to run at least 2 percent faster or 2 percent slower than the speed of die cylinder 16 when the output of transmission 90 is adjusted, as previously explained, to its full add or subtract condition and, of course, at a fraction of these positions between maximum and minimum. However, it should be understood that a transmission may be selected with a ratio to provide as much as l percent overspeed and 10 percent underspeed if desired although the 2 percent capability is usually sufficient.

Accordingly, by following the very simple operating procedure outlined above, very accurate die cutting is easily attainable.

Although the invention is more effective with anvil covers 36 securely fastened to the anvil cylinder drum 38, the velocity of blanks 40 may be controlled even when conventional free-wheeling anvil covers are used since the covers tend to drag on the cylinder drum and thus the surface velocity of the covers is affected by overspeeding or underspeeding the anvil cylinder.

It should be recognized that the surface velocity of the anvil cover affects the overall velocity of the blank passing between the cylinders thereby controlling the accuracy of cuts made in the blanks. Therefore, it

should be understood that the output of the transmission 70 may be connected to an anvil cylinder cover so as to rotate the cover itself around the anvil cylinder which may be held stationary. Accordingly, reference to driving the anvil cylinder herein shall be deemed to include such an arrangement.

Having thus described the invention in its best embodiment and mode of operation, that which is desired to be claimed by Letters Patent is:

1. Apparatus for controlling the accuracy of cuts made in paperboard blanks passing between a pair of cooperating die and anvil cylinders comprising:

first drive means for rotating said die cylinder at a first selectable velocity;

first mechanical transmission means responsive to said first drive means for rotating said anvil cylinder at a second velocity corresponding to changes in said first velocity and in selected proportion thereto; and

second mechanical transmission means having an input means responsive to said first drive means and having a selectively variable output means responsive to said input means,

said first transmission means being additionally responsive to said selectively variable output means for rotating said anvil cylinder at said second velocity and in preselected proportion to said first velocy.

for controlling the velocity of said blanks.

2. The apparatus of claim 1 wherein:

said first transmission means includes a primary input means connected to said die cylinder for driving said anvil cylinder through said first transmission means at said second velocity corresponding to changes in said first velocity.

3. The apparatus of claim 1 wherein:

said input means of said second transmission means is connected to said die cylinder for driving said selectively variable output means at a velocity corresponding to changes in said first velocity.

4. The apparatus of claim 1 wherein:

said second transmission means includes manually operable control means for selectively varying the output velocity of said output means for rotating said anvil cylinder through said first transmission means at said second velocity in preselected proportion to said first velocity.

5. The apparatus of claim 2 wherein:

said first drive means includes first gear means on an end of said die cylinder; and

said primary input means includes second gear means drivable by said first gear means.

6. The apparatus of claim 5 further including clutch means interposed between said first and second gear means for permitting the rotational position of said anvil cylinder to change with respect to the rotational position of said die cylinder upon the occurence of an excessive torque requirement for rotating said anvil cylinder.

7. The apparatus of claim 1 wherein said first transmission means comprises a harmonic drive type transmission means.

8. The apparatus of claim 1 wherein said second transmission means comprisesa positive infinitely variable type transmission means having manually operable control means for selectively varying the velocity of said output means.

9. The apparatus of claim 1 wherein said second transmission means is adjustable to provide an infinitely variable said second velocity within the range of 10% above and 10% below said first selectable velocity. 

1. Apparatus for controlling the accuracy of cuts made in paperboard blanks passing between a pair of cooperating die and anvil cylinders comprising: first drive means for rotating said die cylinder at a first selectable velocity; first mechanical transmission means responsive to said first drive means for rotating said anvil cylinder at a second velocity corresponding to changes in said first velocity and in selected proportion thereto; and second mechanical transmission means having an input means responsive to said first drive means and having a selectively variable output means responsive to said input means, said first transmission means being additionally responsive to said selectively variable output means for rotating said anvil cylinder at said second velocity and in preselected proportion to said first velocity, for controlling the velocity of said blanks.
 2. The apparatus of claim 1 wherein: said first transmission means includes a primary input means connected to said die cylinder for driving said anvil cylinder through said first transmission means at said second velocity corresponding to changes in said first velocity.
 3. The apparatus of claim 1 wherein: said input means of said second transmission means is connected to said die cylinder for driving said selectively variable output means at a velocity corresponding to changes in said first velocity.
 4. The apparatus of claim 1 wherein: said second transmission means includes manually operable control means for selectively varying the output velocity of said output means for rotating said anvil cylinder through said first transmission means at said second velocity in preselected proportion to said first velocity.
 5. The apparatus of claim 2 wherein: said first drive means includes first gear means on an end of said die cylinder; and said primary input means includes second gear means drivable by said first gear means.
 6. The apparatus of claim 5 further including clutch means interposed between said first and second gear means for permitting the rotational position of said anvil cylinder to change with respect to the rotational position of said die cylinder upon the occurence of an excessive torque requirement for rotating said anvil cylinder.
 7. The apparatus of claim 1 wherein said first transmission means comprises a harmonic drive type transmission means.
 8. The apparatus of claim 1 wherein said second transmission means comprises a positive infinitely variable type transmission means having manually operable control means for selectively varying the velocity of said output means.
 9. The apparatus of claim 1 wherein said second transmission means is adjustable to provide an infinitely variable said second velocity within the range of 10% above and 10% below said first selectable velocity. 